In products related to electronic systems, such as the multi-layer circuit boards, LTCCs, ICs, thick-film ceramics, thin-film ceramics and silicon-on-glass substrate processes, the printed circuit board (PCB), which supports electronic components generally, is a plan substrate which was made up of glass fibers and on which conductive circuitry was printed. With the prevailing trend in electronic products being ‘slim type’ and ‘mini size’, the development of the PCB is inclined to the one with a small-bore diameter, high density, multi-layer and thin circuit. An excellent scheme of increasing the density of the circuit is the multi-layer circuit board.
Once the number of layers of the PCB is increased, it results such serious interference that signal transmission lines must be through each layer. Further, since the prevailing trend in electronic products is high frequency, high transmission speed and a higher requirement for accuracy of the transmission impedance and efficiency of the signal transmission, the impedance dis-matching results in the signal bounce to cause many problems. In light cases, the system will work unstable, and in serious cases, the system will be damaged. In consequence, the circuitry design for the PCB is aimed at its width and distance of the signal transmission lines, further, at setting up the balanced impedance design. However, the circuitry design for the conventional PCB is chiefly and simply aimed at the signal transmission in a plane and not aimed at the signal transmission in a perpendicular. A difficult point of the circuitry design for the multi-layer circuit board is the signal transmission between the different layers in a perpendicular direction, so it will avoid vertically transmitting the signals over the vias between the layers in a perpendicular direction in many high-frequency circuitry designs.
In the U.S. patent application of publication No. 2004/0053014, a multilayer printed board is introduced. It has first and second signal transmission lines and first and second ground layers. A signal via is connected between the first and second transmission lines. Ground vias are connected between the first and second ground layers, and they are near to the signal via but not connected with it. The end of the first ground layer protrudes with respect to the second ground layer and extends nearer to the signal via than the second ground layer. Thus, it is possible to stabilize the characteristic impedance of the first transmission line. Further, the first and second ground layers are interlaced, so that it is procured to control the characteristic impedance effectively. However, this circuitry design is complicated, so that flexibility in circuit application is decreasing and precision control of its PCB is not easy.